To condense every last particle of gas in a one cubic meter chamber a cold sink would have to be maintained for an indefinite time and or a getter fired as in CRT,s despite thermal leakage.To remove EVERY particle would take an infinite time and energy.

Given a box that was substantially larger than one cubic meter, and ignoring quantum effects for the moment, one could reduce the number of particles in the box to the point where a given cubic meter of it probably has no particle in it at any given point in time (but this would take a lot of energy, and is of limited utility).

In "Physics Land" (ie everything behaves in an ideal manner), assume that you have a square tube with a 1m x 1m hole, open at one end, and a perfectly-fitting square plug that can move along the square tube. To produce a cubic meter of vacuum, you just need to pull the plug out by 1 meter.

Now, Energy=Force x Distance=100x103N x 1m = 100kJ.

Of course, as other respondents have noted, there is no such thing as a perfect seal, moving a plug is likely to scrape off atoms (and larger lumps), and there is no material which has zero vapour pressure. So the above is a "best possible" answer.

It would be interesting to know how much power is expended per cubic meter to maintain the near perfect vacuum in the LHC As far as I can ascertain the refrigeration system of the LHC consumes 170 KW to maintain 9000 cubic meters of vacuum which equate to about 19w/m^3 of course the initial pump down from atmospheric pressure would have required a considerable amount of energy.

In "Physics Land" (ie everything behaves in an ideal manner), assume that you have a square tube with a 1m x 1m hole, open at one end, and a perfectly-fitting square plug that can move along the square tube. To produce a cubic meter of vacuum, you just need to pull the plug out by 1 meter.

Now, Energy=Force x Distance=100x103N x 1m = 100kJ.

Of course, as other respondents have noted, there is no such thing as a perfect seal, moving a plug is likely to scrape off atoms (and larger lumps), and there is no material which has zero vapour pressure. So the above is a "best possible" answer.

Nice response, Evan. I was going to post the exact same thing. Great minds think alike!